Our primary effort this next year will be to continue our investigation of the metabolism of the myocardium using a mass spectrometer for pO2 and pCO2 determination. We will be studying a number of different cardiac operative procedures particularly involving anoxic arrest with and without hypothermia and also comparing the fibrillating-bypassed heart with the beating-bypassed heart while we evaluate the myocardial pO2 and pCO2. We will also be attempting to correlate surface EKG recordings with local pO2 and pCO2 determinations in the myocardium. In addition, we will continue to work with the development of the monocusp leaflet prosthetic valve.